1. Field of the Invention
The present invention relates to a disk hold device which can be applied to a compact disk drive device or the like.
2. Related Art
Conventionally, as an ordinary disk hold device which has been used in a compact disk drive device and the like, for example, there is known a device which clamps a disk by means of a turn table and a disk hold member such as a magnet to thereby hold the disk, as disclosed in Unexamined Japanese Utility Model Publication sho. 61-28138. The disk hold device of this type is mainly applied to a stationary disk drive device designed mainly for house use. However, if the disk hold member is applied, as it is, to a portable disk drive device which must be constructed thin, a thin portable disk drive device cannot be realized due to the disk hold member. Therefore, in order to solve such problem, there has been conventionally proposed a disk hold device in which a plurality of balls are disposed in the center portion of a turn table such that they project out in the radial direction of the turn table and a disk is held on the turn table by means of the projecting urging forces of the balls. Such device is disclosed, for example, in Unexamined Japanese Utility Model Publication sho. 53-96806. Description will be given below concretely of a conventional disk hold device of this type.
In FIGS. 12 and 13, a turn table 81 is rotationally driven by a motor 89. In the center portion of the turn table 81, there is provided a peripheral wall 82 which projects upwardly and is formed integrally with the turn table 81 center portion, and a cap-like ball hold member 83 is fitted with the peripheral wall 82, whereby the ball hold member 83 can be fixed onto the turn table 81. The ball hold member 83 serves as a disk mount part and the outer diameter of the ball hold member 83 is equal or slightly smaller than the diameter of a central hole of a disk 40. The ball hold member 83 includes in the inside thereof three groove-like ball guides 88 which are disposed at equal intervals with respect to the peripheral direction thereof and extend in the radial direction thereof. In each of the ball guides 88, there is disposed a ball 84 which can be moved along the ball guide 88. Also, each ball guide 88 has an opening which is open to the outer peripheral surface of the ball hold member 83 and each ball 84 is forced toward outwardly in the radial direction thereof by a coil spring 85 which is disposed within the ball guide 88. Each ball guide 88 also has two side walls 86 in the vicinity of the opening and the two side walls 86 are projected inward in the radial direction to thereby prevent each ball 84 form slipping off. Each of the balls 84 is urged outward in the radial direction thereof by the coil spring 85 so that part of the ball 84 is projected out from the opening of the ball hold member 83. Between the projection position of the ball 84 and the disk carry surface of the turn table 81, there is secured a proper dimension which is calculated on the basis of the thickness dimension of the disk 40, so that the ball 84 forms an engagement member for engaging the disk 40.
To load the disk 40 onto the turn table 81, as shownby a one-dot chained line right in FIG. 13, the central hole of the disk 40 is fitted with the outer periphery of the ball hold member 83 and is then put onto the respective balls 84, the disk 40 is pressed by fingers, and while the balls 84 are being retreated inwardly in the radial direction against the urging force of the spring 85, the disk 40 is put on the turn table 81. If the disk 40 is put on the turn table 81, then part of the ball 84 is projected out from the opening of the ball hold member 83 by the urging force of the spring 85, the upper edge portion of the central hole of the disk 40 is pushed by the urging force given to the ball 84 and thus the disk 40 is pressed onto the turn table 81, so that the disk 40 can be rotated integrally with the turn table 81.
On the other hand, to remove the disk 40 from the turn table 81, as shown left in FIG. 13, one finger is put onto the ball hold member 83, another finger is applied to the outer periphery of the disk 40 shown by a two-dot chained line, and then the outer peripheral portion of the disk 40 is lifted up forcibly. By doing so, the edge portion of the central hole of the disk 40 retreats the ball 84 inwardly in the radial direction against the urging force given by the spring 85, so that the disk 40 can be removed from the ball hold member 83.
Also, as a second example of the conventional disk hold device, there is also known a device which is disclosed in Unexamined Japanese Patent Publication sho 60-237672. The second conventional disk hold device is shown in FIGS. 14 and 15. The device includes a turn -table 90 which can be rotatively driven by a motor 92 and a plurality of elastic pieces 91 which respectively extend from the center portion of the turn table 90 and projects upwardly. The elastic pieces 91 are arranged along a circumference which is substantially equal in diameter to the center hole of the disk 40 and each of the elastic pieces 91 is normally, or in its natural state, projected in part outwardly in the diameter direction. And, as shown in FIG. 15, if the upper ends of the respective elastic pieces 91 are pressed simultaneously, then the elastic pieces 91 are flexed inwardly against the elastic forces thereof.
In the conventional disk hold device shown in FIGS. 14 and 15, to load the disk 40, the center hole of the disk 40 is fitted with the upper portion of the respective elastic pieces 91 and then the disk 40 is pressed down with a finger. The upper inclined surfaces of the respective elastic pieces 91 are pressed against the edge portion of the center hole of the disk 40 and thus the elastic pieces 91 are flexed inwardly in the diameter direction, so that the disk 40 is put onto the turn table 90. If the disk 40 is put on the table 90, then the elastic pieces 91 respectively spread toward their original positions due to their own elastic forces and the returning forces of the elastic pieces 91 cause the projected portions of the middle portions of the elastic pieces 91 to press against the upper edge portions of the center hole of the disk 40, so that the disk 40 is pressed onto the turn table 90 and thus the disk 40 can be rotationally driven together with the turn table 90. On the other hand, to remove the disk 40 from the turn table 90, as shown in FIG. 15, the upper ends of the respective elastic pieces 91 are pressed simultaneously with fingers to thereby flex the respective elastic pieces 91 inwardly in the diameter direction and then the disk 40 may be lifted up.
As shown in FIGS. 12 and 13, according to the conventional disk hold device, due to the fact that the disk is loaded and unloaded forcibly against the urging forces of the balls, that is, the disk cannot be loaded and unloaded lightly, there are found the following inconveniences: there is a possibility that the disk cannot be loaded firmly; the recording surface of the disk may be clamped with fingers and may be stained; and, the disk may be damaged. These inconveniences depreciate the commercial value of the disk hold device.
Also, in the conventional disk hold device as shown in FIGS. 14 and 15, because the disk is loaded forcibly against the elastic forces of the elastic pieces, there are found defects which are similar to those found in the conventional disk hold device shown in FIGS. 12 and 13.